Packed-bed cocurrent up-flow reactors gave better results than conventional trickling flow reactors in hydrodesulfurization of heavy oil. To find the characteristics of this up-flow type reactor, liquid-phase mass transfer coefficient, gas-liquid interfacial area and gas holdup in a column packed with 0.1, 0.28 or 0.43 cm glass beads were studied using the oxidation reaction of sodium sulfite.
Experiments were carried out at a reaction temperature of 20°C. Superficial liquid and gas velocities based on empty column, u
l and u
g, were 1-6 and 0.5-6cm/sec, respectively, for any size of glass beads. With the values of u
l and u
g, glass beads bed remained stationary, expanded or fluidized.
Stagnant gas holdup was observed under the condition of u
l<u
lmf (minimum fluidization liquid velocity).
It was found that the stagnant gas holdup was almost ineffective on mass transfer. Volumetric mass transfer coefficient, k
La, and gas-liquid interfacial area, ", were well correlated with dynamic gas holdup, ε
gd, which was a difference between total and stagnant gas holdups. When u
l< u
imf, the correlation was represented in a simple equation of k
La=f
pε
gd (f
p: constant depending on particle size, d
p).
k
La was found to be mainly affected by gas-liquid interfacial area. Larger packing particles gave larger values of k
La. They were larger than those in bubble columns when d
p≥0.28 cm and smaller when d
p=0.1cm.
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